In motor vehicles, dipsticks are employed for purposes of visual inspection of the quantity (and to a lesser degree of the quality) of transmission fluid located within a closed transmission case of a motor vehicle. In general, transmission cases of motor vehicles commonly are provided with an opening leading from external of the transmission case into the interior of the case. Often this opening is provided with a fitting, such as a hollow tube. A first end of the tube is mounted in the opening leading into the transmission case. The tube extends from the fitting to a termination location within the engine compartment of the vehicle, but remote from the transmission case. Thus, the open terminal end of the tube is readily accessible within the engine compartment of a motor vehicle. An elongated removable dipstick may be inserted into the terminal end of the tube and into the interior of the transmission case. Within the transmission case, the end of the dipstick becomes immersed within the fluid disposed within the case. The extent of insertion of the dipstick into the case is limited to a constant value established commonly by some form of stop on the dipstick which engages the terminal end of the tube to limit that distance by which the dipstick may be inserted into the case. Such extent of insertion distance is thus maintained constant over each and every time the dipstick is inserted into the case. By this means, upon withdrawal of the dipstick from the case, the level of fluid on that end of the dipstick which is inserted into the case is indicative of the level (quantity) of fluid within the case. Other than during the action of checking the level of fluid with the case, the dipstick is stored within its tubular housing.
As noted, commonly, such dipsticks are removably mounted within an elongated tubular housing which is itself anchored at one end thereof within the opening through the transmission case. Such tubular housing commonly extends from the transmission case upwardly to terminate at a location, commonly within the engine compartment of the vehicle, wherein the dipstick is readily grasped for insertion into and withdrawal from its tubular housing and the transmission case. For example, the outboard terminal end of the dipstick housing commonly may be anchored to a suitable location on the engine or on the fire wall or other element of the motor vehicle within the engine compartment of the vehicle to ensure rigidity of the tubular housing and its enclosed dipstick during operation of the motor vehicle. Dipsticks commonly are secured within their tubular housing employing some form of structure suitable for grasping with one's hand for removal and reinsertion of the dipstick relative to its housing. This structure may include an element which is frictionally slidably received within the outboard end of the tubular housing and serves in part to seal off the open outboard end of the housing. These devices are prone to leakage of transmission fluid from the tubular housing and fail to ensure the retention of the dipstick within the housing under certain vehicle operating conditions.
In certain motor vehicles, such as racing cars, the operation of the vehicle builds up substantially inordinate pressure within the transmission case. Such pressure levels may be sufficient to “blow out” a prior art dipstick from its elongated tubular housing with obvious disastrous results which may include starting a fire within the engine compartment of the vehicle. Also, there exist the problems associated with oil leaking onto a race track, resulting in slick tires, crashes and monetary penalties.
Further, in racing cars in particular, transmissions are not uncommonly subjected to forces sufficient to cause partial or complete operational failure of the transmission. Upon such failure of the transmission, it is common for the mechanic team for the racing car, in the course of a given race, to change out the entire nonfunctional transmission and replace it with an operational transmission. Obviously such transfer of transmissions must be completed within a minimum of time. In the prior art, precious seconds may be consumed in connection with the removal of a transmission dipstick and its housing from a “blown” transmission and replacement of the same with a new housing (and dipstick) while at the same time trying to minimize the time consumed in replacing the overall transmission.